High torque retention heat insulative gasket structure

ABSTRACT

A gasket structure permitting the selective variance of components thereof whereby high torque retention, heat insulating and fluid-tight sealing is obtained. The specific disclosure and application of use is in a gasket-heat-insulating assemblage for providing insulating and sealing functions between, for instance, the throttle body and bowl or the throttle body and the manifold of an internal combustion engine carburetor assembly. By increasing the density of the heat insulating member at the bolt hole portions by which the member is retained in the assemblage, as by means of densification or the provision of a suitable insert member, torque retention and the spring effect of the member may be controlled. Additionally, by providing gasket layer components on one or both sides of the insulating member, especially where one is furnished with a sealing band, fluidtight sealability in the intended field of use is maximized. Methods for forming specific specific constructions are also disclosed.

Uited States Patent Farnam et a1.

[ HIGH TORQUE RETENTION HEAT INSULATIVE GASKET STRUCTURE [72] Inventors:Robert G. Farnam, New Libson; Michael T. Passarella, Wisconsin Rapids,both of Wis.

[73] Assignee: F. D. Farnam C0.

[22] Filed: Sept. 29, 1970 [21] Appl. No.: 76,459

Related U.S. Application Data [63] Continuation-impart of Ser No. 66958,Aug. 26,

[56] References Cited UNITED STATES PATENTS 2,116,000 5/1938 Peterson.277/227 Victor ...277/235 B 1151 3,655,2w 1451 Apr. 11, W72

Primary Examiner-Robert 1. Smith Attorney-Mann, Brown, McWilliams &Bradway [5 7] ABSTRACT A gasket structure permitting the selectivevariance of components thereof whereby high torque retention, heatinsulating and fluid-tight scaling is obtained. The specific disclosureand application of use is in a .gasket-heat-insulating assemblage forproviding insulating and sealing functions between, for instance, thethrottle body and bowl or the throttle body and the manifold of aninternal combustion engine carburetor assembly. By increasing thedensity of the heat insulating member at the bolt hole portions by whichthe member is retained in the assemblage, as by means of densificationor the provision of a suitable insert member, torque retention and thespring effect of the member may be controlled. Addi-' tionally, byproviding gasket layer components on one or both sides of the insulatingmember, especially where one is furnished with a sealing band,fluid-tight scalability in the intended field of use is maximized.Methods for forming specific specific constructions are also disclosed.

24 Claims, 11 Drawing Figures Patented A ril 11, 1972 3,655,210-

' 3 Sheets-Sheet 1 frz en/Z671:- Rdker Z G. F'armm Patent ed April 11,1972 3,655,210

3 Sheets-Sheet 3 Patented April 11 1972 3 Sheets-Sheet 5 7/ gym Wm I/VlE/VTORS.

ROBERT a. FAR/VAM MICHAEL T. PAssA RELLA HIGH TORQUE RETENTION HEATINSULATIVE GASKET STRUCTURE This application is a continuation-in-partof our application, Ser. No. 66,958 filed Aug. 26, 1970.

BACKGROUND OF THE INVENTION Todays high-powered and sensitive internalcombustion engines have produced unique carburetion problems. Since mostmodern cars have low silhouettes, insulation under the hood, andrestricted air ventilation over the engine, the tendency for temperaturebuild-up in the carburetor is substantially increased, particularly whenthe engine is turned off after normal car operation. If the heatbuild-up is enhanced through conduction from the intake manifold to thecarburetor, the problem is even greater, and hence the need or adequategasket insulation from the intake manifold to the carburetor throttlebody, and in some cases from the throttle body to the fuel bowl.

Along with the need to insulate the carburetor from engine heat is theneed to provide a structure that will also effect sealability betweenthe respective flanged parts in which the insulating structure is used.Thus, where it is desired to use an insulating structure between thethrottle body and the intake manifold, due regard must be given to theprovision of fluidtight seals at the juncture surfaces of thesecomponents. Along with the insulating and sealability requirements forthe above described structure or member, it is necessary to impart tothat structure high torque retention characteristics so that, throughlong periods of usage under service conditions, the components of thecarburetor assemblage will remain in fluidtight relationship or arecapable of being put back into such condition even when one component isremoved from the other during various periods of servicing. Theinsulating-sealing structure must also possess the ability to performthese essential functions without creating distortion in mating metalparts between which it is placed, the metal parts usually being softductile materials, such as aluminum or zinc. By distortion is meantthat, when an insulating-sealing structure is used between opposedflanged members, the bolting of one member to another with theinsulating-gasket structure therebetween, bowing, arcing or other unevenmating of the components will result. Many times a structure that isclamped between two others produces a so-called spring effect, tendingto distort one or both of the mating surfaces of opposed members.Obviously, distortion is quite undesirable in that it breaks thefluid-tight engagement or seal between opposed mating surfaces, and mayalso cause actual breakage of the throttle body adjacent to the boltholes. To meet the aforedescribed criteria and overcome undesirableconditions found in todays automotive environment is the subject matterof this invention.

The prior art has suggested the use of one or more members for effectingthermal insulation, fluid sealing, torque retention and minimization ofdistortion in the highly sensitive carburetor bowl assembly of aninternal combustion engine. However, for the most part, thesesuggestions have been unable to meet and satisfy all of the requirementsnecessary to provide insulating and sealing qualities, while maintaininghigh torque retention. Where one problem was solved, an undesirable oneoffset it, and the selective and independent control of the variablesintrinsic to the overall problem was not obtainable. It is now believedthat a gasket heat-insulating structure is available meeting all of thecriteria dictated for satisfactory use in the carburetor assemblage, allof which is attained within economically feasible boundaries.

SUMMARY OF THE INVENTION In an exemplary embodiment, this inventionpertains to an automotive gasket-insulator structure comprising an atleast two-component assembly of a first member of heat-insulativecharacter and a second member of fluid-sealing character, wherein thefirst member defines peripheral portions adapted to encircle and beretained within the assemblage of use by retaining means such as boltsand the like, and wherein the density of these portions is substantiallygreater than the density of the remainder of either of the said members.More specifically, the invention pertains to a heat-insulative andfluid-sealing gasket structure comprising a heat-insulative member ofselected thickness and configuration generally having a central openingand having a plurality of spaced bolt holes therethrough, the holesbeing peripherally spaced therearound. The bolt holes in one embodimentare larger than are necessary to accommodate the bolts and each has anon-metallic, generally congruent, annular insert member therein of highstrength and low thermal conductivity so as to form a properly sizedbolt hole. A layer of gasket material is positioned on at least one sideof the heat-insulative member and generally is of the sameconfiguration, and it may be secured to the heat-insulative member by anadhesive bond. A continuous sealing bead may be fashioned from a portionof one of the gasket layers inward of and around the central opening ofthe structure, and the sealing bead is of considerably less density thanthe remainder of the gasket layer from which it is formed, therebylending considerable resilience and conforrnability to the sealing beadin order to aid and effect sealing of the carburetor assemblage in whichthe structure is used. The invention is also directed to specificmethods of fabricating the above referred-to members.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration ofhow the structures of this invention are used;

FIG. 2 is a perspective view of one of the embodiments of the inventionas it might be applied to the FIG. 1 environment;

FIG. 3 is a fragmentary, sectional view in cross section taken along thelines 3-3 of FIG. 2;

FIGS. 4A and 4B are fragmentary views in cross section illustratingvarious embodiments of the invention; and

FIGS. 5A and 5B illustrate in somewhat exaggerated and simplified crosssection a component of the structure depicted in FIG. 3;

FIG. 6 illustrates still another embodiment of the invention;

FIG. 7 is a sectional view in cross section taken along lines 7 --7 ofFIG. 6;

FIG. 8 is an expanded view in cross section of the components used toform the embodiment of FIG. 6;

FIG. 9 is a cross section of the embodiment of FIG. 6 together with twoflanges and a bolt.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawingswherein like numerals of reference will designate like elementsthroughout, and referring specifically to FIG. 1, the intended field ofuse for the inventive structures of this invention is illustrated. Itwill be noted that the conventionally-found carburetor assembly 2 havingthe usual air filter or horn 4 is secured by a wing nut to thecarburetor bowl 12, which in turn is secured by bolts 5 to the throttlebody 14, the latter being secured by bolts 6 to the intake manifold, asshown at 8. This is a very diagrammatic illustration but will serve thepurposes to show that the heat-insulating gasket structure 10 of thisinvention is positioned between the flanged portions 3 and 7 ofcomponents 2 and 8, respectively, so as to prevent heat build-up fromthe remainder of the engine (not shown) in the sensitive carburetionarea. By the provision of the structure 10, distortion of the flangedmating areas 3 and 7 of components 2 and 8 is substantially prevented; ahigh degree of torque retention is maintained; and last, but not least,effective fluid-tight sealing is obtained. This latter facet isimportant when considering the low vaporization temperatures of fuelhydrocarbons that are normally consumed in the operation of internalcombustion engmes.

Referring to FIG. 2, the preferred type of heat-insulating gasketstructure that may be used in the particular environment shown in FIG. 1is depicted (although it should be understood that the structures ofthis invention may also be used between the sensitive throttle body 14and carburetor bowl 12). Here, heat-insulating gasket structures 16 hasan outer configuration generally conforming to the size and shape of theflanged surfaces that it will be positioned between. It will be notedthat there are spaced tab, ear or bolt hole portions, such as 18, andcentral aperture or opening 20 forming the interior of the structure.Spaced inwardly from bolt hole portions 18 and radially from centralopening 20 is sealing bead 22, the specifics of which will behereinafter detailed.

The heat-insultaing gasket structure 16 is fabricated in this particularinstance of a central core member or laminate 24, here illustrated asbeing composed of two thicknesses 24a and 24b being secured to oneanother by an adhesive bond layer such as 26. Laminate 24 may comprise asingle or a plurality of individual laminae and should be of low thermalconductivity. A satisfactory type of material has been found to be aphenolicresin impregnated vegetable fiberboard having on either side acongruently shaped gasket layer 28 and 30 of a suitable, conformablegasket material, the specifics of which will be detailed in thefollowing commentary. Gasket layers 28 and 30 are adhered to elements24a and 24b of laminate 24 by an adhesive layer, omitted for purposes ofclarity but similar to layer 26 between elements 24a and 24b.

Each of the bolt hole, ear or tab portions 18 is provided with anoversized hole or aperture, such as 32, within which annular reenforcingmember 34 is firmly held by friction and/or chemical bonding. Member 34is also provided with an aperture, such as 36, which forms a sized bolthole opening to receive retaining bolts 6 to be used in the finalassemblage to maintain the flanged components of the carburetor, withthe gasket 16 therebetween in firm, rigid relationship. The specifics ofmember 34 will be described in detail later.

The bottom gasket layer 30 is essentially planar and coextensive withthe laminated core member 24, but may, if found desirable, be providedwith a sealing bead similar to bead 22 located on the upper planarsurface of structure 16 and also being formed of the same material asgasket layer 28. While bead 22 is formed of the same material as gasketlayer 28, it is or a less dense quality so as to be compressible orconformable in the carburetor assemblage. Sealing bead 22 may take anyshape, depending upon the configuration of the two mating carburetorcomponents between which gasket structure 16 is to be used, butgenerally, it will be continuous in form. In some instances, a similartype bead around the apertures 32 formed in tab portions 18 may be foundto be desirable. Bead size and shape will be governed by specific enduses, but generally the bead may have a height within the range of about0.0050.0l inch, and in the preferred form will have a rounded crosssection about 0.0500.080 inch wide. Other heights and cross-sectionalconfigurations are, of course, contemplated.

In the FIG. 2 embodiment the insert reenforcing member 34 is shown as asolid member of synthetic, non-metalic material, but it may also be, aswill immediately become apparent, a laminated structure, a metal member,or one of solid molded character. A wide range of materials, sizes andshapes will also serve desired purposes.

The embodiment of the invention just described is a preferred one, butthere are other arrangements contemplated, and some of these are shownin FIGS. 4A and 4B. Referring specifically to these Figures, it will benoted that a heatdnsulating member or core 40 is shown as fabricated ofa single, unitary board, but again, it may be a laminated one as earlierdescribed with two or more individual layers or components. For purposesof illustration, however, the central core 40 is illustrated as a singlethickness comprising low thermal conductivity material such asresin-impregnated vegetable fiberboard of the type that is commerciallyavailable about 0.090 inch thick, but which is reduced, when densified,at the ear or tab portions about 0.015 inch as by coining or highpressure compression. The primary distinction in this embodiment is thatbolt or tab portions 18differ from those tab portions 18 shown in FIGS.2 and 3. In each of the illustrations, a gasket layer is used on bothtop and bottom of the central core member 40, but it should beunderstood that only one such gasket layer with, or without sealing beadon either upper or bottom surface may be used under certain conditions.

Referring specifically now to FIG. 4A, a bolt hole tab portion 18'isshown as having a highly densified construction as indicated by theheavy cross-hatching. This extreme densification is obtained bypressing, coining, or otherwise decreasing the volume of the fiberboard40 in the tab area l8'of the bolt hole opening. Upper gasket layer 42 isprovided with a sealing bead, such as 44, of less density, and hencemore conformability than the remainder of the surrounding gasket layer42. It should be noted also that gasket layer 42 is of greater thicknessin the area of the core densification and preferably has approximatelythe same density of the bead 44. Positioned on the bottom of coreinsulating board 40 is another gasket layer, such as 46, and iscoextensive with the tab portion 18, and each of the gasket layers 42and 46 may be secured to the core 40 by means of an adhesive bond layeromitted for purposes of clarity.

Referring now to FIG. 4B, a structure similar to that shown in FIG. 4Ais depicted, with the exception that densification of the fiberboardcore 40 in the area of the tab 18is carried to an extent so as to formdepression or recess 48 in the outermost portion of tab 18. The gasketlayers 42' and 46, as well as sealing head 44, are the same as earlierdescribed for the FIG. 4A embodiment, except that the gasket 42 ispreferably of uniform thickness and density except for the head 44. Inorder to obtain high torque retention and proper sealing when the unitis clamped between mating flanges of the carburetor assembly, an annularinsert member or washer, such as 50, is fitted and press fitted orotherwise secured in recess 48. Obviously, because it is desired to cutdown on heat transmission between metal components in which thestructures of this invention are used, it is desirable to use a metal oflow conductivity for insert 50, if a metal washer is to be used, butstill preferred is a high density, highly compressed resin-impregnatedasbestos fiber material or molded plastic material of low thermalconductivity.

Referring now specifically to FIGS. 5A and SE, a preferred mode ofobtaining densification or high torque retention is by means of aninsert of a type that may be used especially in the FIGS. 2, 3 and 4Bembodiments of the invention. In FIG. 5A, the insert 60 is shown ascomprising a plurality of laminae 62 of a thin, porous asbestos paperconstruction with long asbestos fibers 64 being laid perpendicularly tothe longitudinal axis of the central aperture 66. In this particularstructure, the individual lamina 62 are placed in a vertical stack andthen subjected to a vacuum impregnation process, the impregnationutilizing a heat-resistant thermosetting resin such as the phenolicresins to form interconnecting links, such as 68, between the individuallaminate layers 62. These links 68 are merely diagrammaticallyillustrated, and it is not intended to show in micro-photographicfashion the impregnated structure that would actually result after suchimpregnation process. Sufiice it to say, however, that an annular ortubular laminate member 60 is formed having a multiplicity ofinterconnecting resin links, such as 68, and being totally encased by alayer of the same material on the outside and, indeed, the insidesurfaces, such as shown. After the plurality of lamina 62 have beenvacuum impregnated or otherwise interconnected with phenolic resin, themember 60 is highly compressed and densified to produce a member of highstrength, good torque retention, and low heat or thermal conductivity.

The FIG. 5B embodiment shows another construction for an insert member70, and such member is depicted as comprising a plurality of asbestosboard lamina 72 which have been impregnated or dipped in a phenolicresin so as to saturate its pores and having adhesive phenolic resinlayers 74 therebetween, and fabricated under high pressures to produce ahighly compressed, densified member having similar characteristics asmember 60 in FIG. 5A.

It should be understood that the products described in FIGS. 5A and 5Bare suitably post-cured and are adapted for use for the insert 34 ofFIG. 3 or the washer 50 of FIG. 48.

THE CORE OR INSULATING MEMBER Because it is highly desirable to providesuitable insulation between carburetor components as referred to herein,the thickness of the insulating member will be dictated by spacerequirements and structural characteristics of the carburetor as well asthe temperatures developed in the carburetor area. Generally speaking,the insulator member will be one having a low heat conductivity and willhave a K value of approximately 1.0 1.2, but this will vary dependingupon other factors. Generally speaking, the insulating member may bemade up of one or more layers or lamina depending upon space and otherrequirements and the form in which the insulative materials arecommercially available. The materials of construction for the insulativeor core member may be any of those presently regarded in the art asmeeting the aforedefined requirements. Materials contemplated includethe well-known synthetic materials, but because of economic factors, aresin reenforced vegetable or similar fiberboard is both practical andeconomical. Generally, such materials may be described as semi-porousfiberboard reenforced with thermosetting resin. In some of theillustrated specific embodiments, particularly where portions of theboard are to be densified or materially compressed, compressibility ofthe core or insulator member becomes important. Generally speaking, thethickness that the insulator member may take will, as earlier indicated,be dictated by other considerations, but in the specific embodimentsdisclosed a fiberboard core of about 0.030 0.125 inch thick will be mostpractical. Because a material, such as fiberboard, reenforced withthermosetting resin, is compressible, its torque retention capabilitywill be relatively low, somewhere on the order of 40 to 50 percent,measured at a 250 F temperature using an ASTM, F 38, Method B test for a0.125 inch thick core; thus, the need for densification in the bolt holeportion, or the alternate use of an insert of one type or another aspreviously disclosed, is highly desirable. Due regard for thicknessreduction where densification of the core itself is contemplated isnecessary, such reduction being typically in the range of about 0.015inch.

THE GASKET LAYERS In general, the materials contemplated in order toperform the fluid-tight sealing function in the structures of thisinvention are those materials commonly used in the gasket art becausethese materials have proven themselves in service to be able towithstand the rigors of service conditions generally found in carburetorenvironments. Typical such gasket materials are those made in accordwith the teachings of Kao U.S. Pat No. 2,676,099, issued Apr. 20, 1954.A satisfactory type of gasket material has been one found to be using amineral fiber and cured nitrile rubber. Such material is available fromthe F. D. Farnam Co. under the trade name Kaobestos 66015. Other gasketmaterials and the like may be used, as disclosed in U.S. Pat. to Farnamet al. No. 3,158,626. Other materials for other applications are alsocontemplated. Typical thicknesses of suitable materials will be withinthe range of about 0.020 inch which will be reduced or compressed toabout 0.015 inch during bonding thereof to the core.

Generally speaking, however, the gasket materials should be ofelastometric material so as to be easily compressible in order toachieve fluid-tight sealing under light clamp loads, and generallyshould be those that are rather resilient, or bulked, that is, somewhatlight in density so as to be capable of being compressed to form. Wheredesired, a sealing bead of sufficient size may be provided to contributeto the sealing function. Also, because it is desired to fashion astructure which will provide fluid sealing, the gasket layer or layersshould be conformable enough to take up the differences in matingtolerances generally found in carburetor components, and also be of amaterial which has low heat transmissibility.

A sealing bead, in order to effect efficient fluid-tight sealing, may beformed during the sandwiching or molding process of the insulatinggasket structures of this invention. The bead may be formed on one orboth gasket layers, although it has been found that the utilization of asealing bead on the upper gasket layer will normally suffice. This beadmay take many configurations, but generally, one having a roundedcross-sectional shape of a height of about 0.005 0.015 inch and a crosssection width of about 0.050 0.080 inch has been found to besatisfactory. When the bead is formed of the same material as the gasketlayer adjacent thereto, the density thereof will be much less than thatof the surrounding gasket material for the reason that it is notcompressed as much during the molding or pressing process as the gasketmaterial layer adjacent thereto. This, then, provides a conformable orresilient protuberance or projection in order to permit satisfactorysealing.

An adhesive bond layer is contemplated for securing both upper and,whereused, bottom gasket layer to the core or insulating member, andtypes of adhesives and the like that may be used may vary considerablyjust so long as they are capable of forming an effective bond and willnot deteriorate under the service conditions contemplated for thestructures of this invention. Generally, the neoprenes have been foundto be capable of forming effective bonds, and the addition of phenolicresins to some of these formulations has also been found to beeffective. A preferred type of adhesive is a phenolic resin and neoprenecombination which is thermosetting at a temperature of about 325 350 F.It is preferred that the adhesive layer bond between the insulatingmember and gasket layer or layers be only that thickness necessary toform an effective bond and no more. Where applied, the bonding materiallayer should not exceed approximately 0.0003 0.0007 inch at any onelayer. These same types of materials may also be used to form theadhesive bond between individual lamina of the core or insulating memberwhere it is desired to build up and have a core insulator of a thicknessgreater than can be made from commercially available stocks.

There are a number of elastomer-resin compositions available, each ofwhich has specific advantages. It is only important that the adhesive becapable of being applied as a continuous thin layer and that it be suchthat it can be dried or partially cured for easy handling prior to thefinal assemblage of the structures of this invention, and that it alsobe capable upon final or ultimate curing or producing a bond betweenadjacent lamina of the core member or between the core member and one ormore gasket layers that will withstand the environmental conditionsfound in a carburetor assemblage. The types of elastomer compositionsfound desirable may be those disclosed in Farnam et al. U.S. Pat. No.3,l58,626.

AREA DENSIFICATION tioned, i.e., area densification of the insulatormember itself at v the area of the bolt holes, as shown in FIG. 4A.Another means of achieving substantially the same results is by densifying this area to the extent that a recess is formed within which anannular or tubular insert mamber may be positioned (See FIG. 48) with orwithout a gasket layer covering, and the member may be of metal, solidmolded plastic, or fabricated from phenolic resin-impregnatedlaminations of asbestos paper, asbestos board and similar suchmaterials. Also the members, inserts or the like, when made of metal maybe very similar to bushings, washers, and similar such structures, andwill be fabricated of steel and similar such metals or preferably lowheat conductivity or K value. Any of the insert members may run half thethickness, three-quarters or the thickness, or greater than the entirethickness of the finished insulator-gasket structure which generallywill be about 0.1 0.120 inch in thickness. In the preferred embodiment,an insert member of asbestos lamina is placed in an oversized bolt holeand retained therein in friction-fit manner and extends about the entirethickness of the finished structure, but in the fabricating process itis of slightly less thickness, say about 0.005 inch, to thereby act as alimiting compression factor in the gasket-insulator structure itself.For instance, because the materials of construction are compressible innature and an insert member either of metal or highly densified asbestosphenolic resin-impregnated asbestos is substantially unyielding incomparison, the insertion of such a member prior to the actual volumereduction, compression or molding of the overall structure will limitthe extent to which the overall structure may be compressed. Morespecific details of this aspect will be delved into under manufacturingtechniques.

In the preferred embodiment, however, where a separate non-metallicinsert is utilized, the insert comprises a plurality of layers ofasbestos paper or asbestos millboard which has been saturated orimpregnated with a thermosetting phenolic resin. Preferably, the numberof laminations is kept to a minimum, but this will generally be dictatedby the thickness or height of the insert that will be used in theparticular insulator-gasket structure. The heat-resistant thermosetting,phenolic resin provides the necessary strength and torque retention, andin a preferred form, the fibers (where asbestos paper or asbestosfiberboard is used) have relatively long lengths and are laid at rightangles to the clamping force, or, in other words, are normal to thelongitudinal axis of the bolt hole which the insert, itself, forms.Other non-metallic fibers will also perform satisfactorily. When alamination has been built up, it will be subjected to a pressingoperation which will materially reduce the thickness to as great as 40and more of its original thickness, thereby producing a highlycompressed and dense non-metallic insert which may be subjected to acuring step to insure total curing of the phenolic resin or othermaterial used in fabricating the insert. Non-metallic inserts usingasbestos fiber and the phenolic resin combination will normally have adensity of approximately 120 pounds per cubic foot, a thermalconductivity or K factor of approximately 2 to 2.5, or thereabouts (ascompared to about 50 for steel), and will have high compression strengthand also chemical resistance to the environment in which theinsulatorgasket structure will be used. Also, they will preferably beable to take a torque load of approximately 15,000 to 20,000 pounds persquare inch without fracture.

FABRICATION TECHNIQUES Keeping in mind the materials used in theinsulator-gasket of this invention, a more comprehensive understandingof the exemplary methods of fabricating the overall structures may nowbe had, taken in conjunction with earlier alluded to manufacturingtechniques.

In the following example, it will be assumed that a structure having adouble lamina core with top and bottom gasket material layers isdesired. Suitable cover stock, generally of a slightly bulkier naturethan is usual (especially where a sealing bead is to be formed), is cutto an appropriate width, this width being dictated by the width of thecore or head-insulating member. In some instances, however, even thecommercially available resin-impregnated fiberboard will have to be cutto size, and thus the size will be dictated by the configuration of theultimate insulator-gasket structure to be formed. After appropriatesizing of, for instance, a gasket layer and the heat-insulating memberboard, a first laminate is formed by taking a continuous roll of coverstock, and laminating it with an adhesive bond material to a sheet ofcore material approximately 90 inches long and one-half the final corethickness, with periodic cutting off from the continuous roll of coverstock to form a plurality of gasket covered core sheets. Thereafter, thepanels will be coated on the side opposite the cover stock with a thincoating of elastomer resin adhesive and then allowed to dry. Aftersuitable drying, the thusly gasket-layered panels may be laminated toone another to form a second laminate by means of the adhesive layer andcut into appropriate widths.

The second or final laminate may then be die-cut into the ultimatestructure configuration that is intended with oversized bolt holeopenings which will later receive non-metallic inserts in order to formproperly sized bolt hole openings. Depending upon the total thickness ofthe insulator-gasket structure, it may be made from two layers of coreboard, or one layer of core board, or more than two layers. If there aremore than two layers, the inner layers of the core board will also becoated on either side with a thin layer of adhesive as just described.

The thickness range of the bonding material requires some control sothat it will not exceed approximately 0.0003 0.0007 inch at any onelayerfDouble this thickness would occur where tow coated surfaces arebrought together.

Next, the sandwich or assemblage is subjected to a hot pressingoperation in a pin mold, the upper mold being provided with a groove toultimately fashion the sealing bead in the upper gasket cover stock.Before initiation of the hot pressing operation, however, the preferredmethod is to insert the non-metallic bushings or inserts which will actas a sizing means for the overall thickness of the final structure,since they are relatively non-compressible in relation to the remainderof the structure. This permits the production of structures of thisinvention to very close thickness tolerances. Obviously, wherewarranted, these inserts may be placed in position after thehot-pressing operation. During the hotpressing operation, the sandwichof members in considerably reduced in thickness, and hence, the insertsmay be slightly less in height than the intended overall thickness ofthe ultimate structure (as indicated at 70 in FIG 3) to thereby insure aproperly sized insulator-gasket member. The bead is best formed by meansof a groove in the upper mold half, and by bulking both the cover stockand the core slightly (within the range of 5 10 percent), and thenbringing the assemblage to full density during the pressing operation,which procedure produces a conformable bead and which provides for easeof forming the bead. Obviously, where it is contemplated that theinsulating member, itself, be densified in the area of the bolt holes,this is accomplished by building up those portions, and thereafterdensifying to a much greater extent than would be the case where themember itself was not be be densified. The formation of a recess withpartial densification and insertion of a metallic or non-metallicpartial insert may, of course, be accomplished at the same pressingstep, as will be apparent from the drawings. Suflice it to say, however,that the insertion of insert elements, where contemplated, may besubsequent to the entire pressing step, or it may be before or at thetime of the mold pressing operation. The hot pressing is carried outover a dwell time, depending upon the thickness in the area of the bondline, at a temperature sufficient to cure, set, or otherwise insurebonding of all of the members making up the structure. Obviously, wherean epoxy resin-type bonding material or adhesive is contemplated, it maynot be necessary to hot-press or to carry on curing at an elevatedtemperature, since such systems normally involve a curing agent orcatalyst not requiring heat, pressure, etc.

Thereafter, the insulator-gasket structure may be subjected to apost-cure, if required, and the insert member 34 may then be pressedinto position, if not already there. This positioning may be done byhand, semi-automatically, etc., and these as well as othermodifications, depending upon the structures involved, will be at oncemake themselves apparent when considering the materials employed and thedesired results to be achieved.

In an alternate procedure, the non-metallic washers are made fromasbestos millboard having long asbestos fibers bound together withstarch or other conventional binder, and the millboard is impregnatedwith phenolic resin, preferably with the aid of vacuum so that the resincontent is from 10 to 30 percent by weight of the board, and ordinarilywithin 20 to 25 percent of such weight. The resin used is awater-alcohol phenolic resin mix. After the board is vacuum-impregnatedwith the phenolic resin, it is dried at a low temperature and stored ina cool room (approximately 30 50 F) to substantially stop resin aircuring.

The washers are then die-cut from the board and dropped into the openingin the gasket and placed in a pin mold, with the plunger which operatesin the area of the pin being offset to accommodate the greater thicknessof the washers. The pin mold is then closed under pressure, but not tooquickly, because it has been found that a certain amount of time isrequired to permit the resin to flow laterally into the adjacent gasketstructure and be bonded thereto at temperatures of about 150 to 350 F.Ordinarily, the time required for this function to take place is on theorder of to seconds.

After the washers are set in the gaskets, the bond lines between thelaminates forming the core and between the gasket covers and the coreare cured at a temperature of approximately 275F for 10 or minutes inorder to degas the material, after which the temperature is stepped upto 300 to 375 in order to get the complete cure.

Of course, the non-metallic washers, instead of being compressed anddensified in the manner described above during the hot-pressing of theentire gasket, may be completely fabricated and cured before the washersare inserted in the insulator gasket, relying upon a press fit tomaintain the washer in place within the gasket.

A modified form of the invention is shown in FIGS. 6 through 9inclusive, and in this embodiment of the invention the core, generallydesignated 85, is made from asbestos millboard and is essentially thesame as the asbestos millboard used in the fabrication of the inserts 34previously described. ln this case, the core 85 is formed by taking twoor more diecut pieces 86 which have been suitably impregnated with thewater-alcohol, phenolic resin mix, and placing them on a heated pin moldwith a washer-like member 87 interposed therebetween (see FIG. 8), andflanked on their outer sides with die-cut gasket pieces 88 and 89. Thecore members 86 have openings 90 corresponding in diameter to the CD. ofthe bolts that will be used for clamping the mating metal flangestogether, and the washer member 87, which is also made of asbestosmillboard and impregnated with the phenolic resin mix, has an interioropening 91 which also corresponds in diameter to that of the clampingbolts. The outer diameter of the washer 87 is roughly the same as thatused for the inserts 34 in the embodiments of the invention shown inFIGS. 2 and 3, and the gasket material 88 and 89 may be the same as thegasket stock shown at 28 and 30 in FIGS. 2 and 3. The gaskets 88 and 89are die-cut with openings 92 which are approximately the same diameteras the CD. of the washers 87, so that when the gasket components arehot-pressed in the pin mold to form the finished gasket, the core 85will be of substantially homogeneous character with protuberances 93 and94 projecting through the openings 92 in the gasket stock, and with thedensity of the core being substantially that of the insens 34. After thehot-press formation of the composite gasket, it may be taken throughfinal cure.

It will, of course, be understood that the core 85 and the gasket covers88 and 89 are die-cut with the other openings that are necessary to formthe configuration shown in FIG. 6 of the drawings.

Either or both of the gasket covers 88 and 89 have a continuous bead 95formed on their outer faces during the compression of the mold, thisbeing accomplished by grooves in the mold faces, as previouslydescribed. Also, in some instances it is desirable to form a number ofsmall protuberances or buttons 96 adjacent to the edges of the gasketfor a purpose that will be later described, these buttons being formedduring the compression of the mold in the same manner that the bead 95is formed.

The fundamental objective in forming a heat insulating gasket in themanner just described is so that when the mating flanges 3 and 7 areclamped together by the bolts 6, as shown in FIGS. 1 and 9, the flangedareas 3 and 7 will bottom on the protuberances 93 and 94, respectively,thereby providing firm clamping together of the parts and high torqueretention, with the head 95 on one or both sides of the gasket providingthe required sealing of the opening 97 from the atmosphere, and with anair space 98 formed between the metal flanges and the gasket structure.The buttons 96, when used, help to maintain that air space when thedistance between the bolts and the character of the flanged areas aresuch that distortion could bottom the flanged areas on the main portionof the gasket structure. It has been found in tests that the heattransmission with a gasket of this type is substantially lessened whenthe mating faces 3 and 7 are not permitted to have face-to-face contactwith the gasket coverings of the composite gasket, and that providingany type of air space, on the order of .010 of an inch or less, theinsulating qualities of the composite gasket are substantially enhanced.

Although it is preferred to actually maintain an air space, such as 98,between the flanges and the composite gasket, some advantage is gainedeven when there is some face-toface contact, as long as suchface-to-face contact is not a truly pressure contact. It is for thatreason that in this embodiment of the invention the outer faces of thecover stock 28 and 30 should be level with the outer faces of theprotuberances 93 and 94, or below these protuberances, as distinguishedfrom the embodiment of the invention shown in FIGS. 2 and 3 where it isintended that the cover stock should be slightly compressed during theclamping of the parts together by the bolts.

Merely by way of specific illustration, and not by way of limitation, ithas been found satisfactory to have the air space 98 on the order offrom about 0.005 to 0.010 inch, with the free height of the sealing beadbeing from about 0.005 inch to about 0.007 inch greater than thedesigned air space, with the bead being compressed during the clampingaction sufficiently to have the mating flanges 3 and 7 bottom on theprotuberances 93 and 94 and provide the desired air space 98. Thebuttons 96, when used, might have a normal free height of approximately0.002 inch to 0.004 inch less than the height of the bead, and would beslightly compressed during the clamping action to assure the desired airspace.

The bead 95 is formed in the same manner as the head 22 of FIGS. 2 and3, and has lesser density than the main body of the cover stock when thegasket is formed, as previously described.

For some installations, it may be desirable to use in place of thebuttons 96 a continuous bead running around the peripheral margin of thecomposite gasket and being located perhaps 1% inch inwardly of theperipheral margin. This bead would be formed in the same manner as thebead 95, but would have a height corresponding to that prescribed forthe buttons 96 and would serve, not only as a limiting abutment toassure the air space remote from the clamping bolts, but also to sealthe exposed faces of the gasket material from the elements and preservethe life of the gasket.

lt should be understood that although it is preferred to have the coremade of asbestos millboard in the manner that has just been described,it is also possible to use the core structure disclosed in the FIGS. 2and 3 embodiment of the invention, with the inserts 34 being sized sothat they are either flush with the covers 28 and 30 or slightly abovetheir level in order to obtain the desired improvement in heatinsulating properties.

When the inserts 34 are above the level of the cover stock, or when theprotuberances 93 and 94 are above such level, the need for the buttons96 is lessened, and in most instances eliminated.

These modifications as well as other embodiments and interchangeableswill make themselves apparent to those working in this art, and suchmatters will not detract from the .essence of the herein disclosedinvention is measured by the appended claims.

The embodiments in which an exclusive property or privilege is claimedare defined as follows:

1. In a heat insulative gasket having a fluid passage-way therethroughand a bolt hole, said gasket comprising a body portion and a bolt holeportion, said bolt hole portion defining an area around the bolt hole ofrelatively high density, substantially non-compressible, material with ak factor in said bolt hole portion of about 3 or less, said body portionhaving at least portions thereof of relatively low density, compressiblegasket material completely surrounding said fluid passageway and lyingin a plane above that of said bolt hole portion.

2. A heat insulative gasket as set forth in claim 1, in which said bodyportion comprises a core and a gasket layer adhered thereto with saidgasket layer having an integral portion thereof constituting saidrelatively low density compressible material surrounding the fluidpassageway.

3. A heat insulative gasket as set forth in claim 2 in which saidintegral elevated portion is in the form of a bead.

4. A heat insulative gasket as set forth in claim 1, in which thedensified bolt hole portion is in the form of a bushing which includes athermosetting resin.

5. A heat insulative gasket as set forth in claim 4, in which thebushing includes asbestos fiber reinforcement for the thermosettingresin.

6. A heat insulative gasket as set forth in claim 4, in which the busingis firmly mounted in a circular opening formed in the gasket.

7. A heat-insulative and fluid-sealing gasket structure comprising aheat-insulative member of selected thickness and configuration having afluid opening and a plurality of spaced bolt holes therethrough, saidbolt holes being larger than necessary to receive bolts and each havinga non-metallic generally congruent annular insert member therein of highcompressive strength and low thermal conductivity to form a sized bolthole, and a layer of gasket material on each side of saidheat-insulative member and having the same general configuration thereofand being secured to said member by an adhesive bond, and a continuoussealing bead on at least one of said gasket layers spaced from andsurrounding said fluid opening with the top of the bead lying above theplane of the insert member.

8. A gasket structure in accordance with claim 7 wherein saidheat-insulative member is of sufficient thickness to inhibit heattransmission between metal components in which it is used.

9. A gasket structure in accordance with claim 8 wherein saidheat-insulative member is of thermosetting resin-impregnated fiberboard.

10. A gasket structure in accordance with claim 8 wherein said annularinsert members are of less or substantially equal thickness with respectto the total sealing thickness of said gasket structure.

11. A gasket structure in accordance with claim 10 wherein said annularinsert member comprises a plurality of laminations of resin-impregnatedasbestos paper.

12. A gasket structure in accordance with claim 11 wherein said asbestospaper comprises long fibers of asbestos laid at right angles to saidbolt openings.

13. A gasket structure in accordance with claim 12 wherein said resin iscured phenolic resin.

14. A gasket structure in accordance with claim 8 wherein said sealingbead is formed by a portion of said gasket layer having a density lessthan the remainder thereof.

15. A gasket structure in accordance with claim 14 wherein said sealingbead is substantially semi-circular in cross section and is ofsufficient size to effectuate substantially fluid-tight sealing whensaid structure is clamped and used in its intended environment.

16. A gasket structure in accordance with claim 15 wherein a secondgasket layer is provided on the opposite side of said heat-insulativemember opposite said sealing bead.

17 A heat insulator gasket for carburetors used in automotive enginesand the like comprising a core member of fiberboard material, and gasketcover stock comprisin elastomenc material bonde to the top and bottomfaces 0 the core, said core and cover stock having a plurality ofaligned openings therethrough for the reception of bolts, said boltholes having the area immediately adjacent thereto characterized byhaving a density substantially greater than the density of the remainderof the gasket, at least one of said cover stock coverings having anelevated continuous bead lying in a plane above that of the densifiedbolt hole areas and located on and above said remainder of the gasket.

18. A gasket as set forth in claim 17 in which the densification in thearea of the bolt holes comprises a non-metallic, highly densified,resin-impregnated and cured material having a heat-insulating factorless than about 3.

19. A heat insulator gasket for carburetors and the like comprising acore member carrying gasket members on the top and bottom surfacesthereof, and with bolt holes and a fluid port extending through thecomposite gasket, said gasket being characterized in that the gasket inthe area of the bolt holes has a k factor less than about 3; thethickness of the gasket in such areas is greater than the thickness ofthe adjacent area of the gasket; a sealing bead is formed on one or bothof the gasket members in the area of and surrounding said fluid port;and wherein the overall thickness of the gasket in the area of saidsealing bead is slightly greater than that of the gasket at said bolthole areas, whereby when the gasket is clamped between flanged members,an air space is provided between one of the flanged members and theadjacent gasket member.

20. A gasket as set forth in claim 19 in which the core member is acured, resin-impregnated, asbestos fiberboard.

21. A gasket as set forth in claim 19 in which the air space isapproximately 0.005 inch to 0.010 inch in depth.

22. A gasket as set forth in claim 19 in which a sealing bead beprovided on both the top nd bottom gasket members.

23. A gasket as set forth in claim 19 in which the free height of thesealing bead is selected to provide about 0.005 inch to about 0.007 inchcompression when the flanged members are clamped together.

24. A gasket as set forth in claim 19 in which an additionalprotuberance is provided on one or both gasket members adjacent to theperipheral margin of the gasket.

UNlTED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent NO.3,655,210 Dated April 11, 1972 Inventor(s) Robert G. Farnam and Michael'I. Passarella It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

In the Abstract, line 15, for "band read bead Column 1, line t, beforethe period, insert now abandoned Column L, line 28, between "gasket" and&2 insert 7 layer Column 11, delete lines 1 and 2, and read instead WECLAIM:

Column ll, line 26, for "busing read bushing Column 12, line 12, for "asecond" read the other Column 12, line 15, after "core" delete member"Column 12, line 19, after "therethrough" insert defining bolt holesColumn 12, line 50, before "provided"'for "be" read is Column 12, line50, between "top and bottom" for "nd" read Signed and sealed this ll thday of November 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,J'R. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents FORM PO-1050'1069) USCOMM-DC 60376-P69 fl U,5. GOVERNMENTPRINYING OFFICE I969 O3GG-334

1. In a heat insulative gasket having a fluid passage-way therethrough and a bolt hole, said gasket comprising a body portion and a bolt hole portion, said bolt hole portion defining an area around the bolt hole of relatively high density, substantially non-compressible, material with a k factor in said bolt hole portion of about 3 or less, said body portion having at least portions thereof of relatively low density, compressible gasket material completely surrounding said fluid passageway and lying in a plane above that of said bolt hole portion.
 2. A heat insulative gasket as set forth in claim 1, in which said body portion comprises a core and a gasket layer adhered thereto with said gasket layer having an integral portion thereof constituting said relatively low density compressible material surrounding the fluid passageway.
 3. A heat insulative gasket as set forth in claim 2 in which said integral elevated portion is in the form of a bead.
 4. A heat insulative gasket as set forth in claim 1, in which the densified bolt hole portion is in the form of a bushing which includes a thermosetting resin.
 5. A heat insulative gasket as set forth in claim 4, in which the bushing includes asbestos fiber reinforcement for the thermosetting resin.
 6. A heat insulative gasket as set forth in claim 4, in which the busing is firmly mounted in a circular opening formed in the gasket.
 7. A heat-insulative and fluid-sealing gasket structure comprising a heat-insulative member of selected thickness and configuration having a fluid opening and a plurality of spaced bolt holes therethrough, said bolt holes being larger than necessary to receive bolts and each having a non-metallic generally congruent annular insert member therein of high compressive strength and low thermal conductivity to form a sized bolt hole, and a layer of gasket material on each side of said heat-insulative member and having the same general configuration thereof and being secured to said member by an adhesive bond, and a continuous sealing bead on at least one of said gasket layers spaced from and surrounding said fluid opening with the top of the bead lying above the plane of the insert member.
 8. A gasket structure in accordance with claim 7 wherein said heat-insulative member is of sufficient thickness to inhibit heat transmission between metal components in which it is used.
 9. A gasket structure in accordance with claim 8 wherein said heat-insulative member is of thermosetting resin-impregnated fiberboard.
 10. A gasket structure in accordance with claim 8 wherein said annular insert members are of less or substantially equal thickness with respect to the total sealing thickness of said gasket structure.
 11. A gasket structure in accordance with claim 10 wherein said annular insert member comprises a plurality of laminations of resin-impregnated asbestos paper.
 12. A gasket structure in accordance with claim 11 wherein said asbestos paper comprises long fibers of asbestos laid at right angles to said bolt openings.
 13. A gasket structure in accordance with claim 12 wherein said resin is cured phenolic resin.
 14. A gasket structure in accordance with claim 8 wherein said sealing bead is formed by a portion of said gasket layer having a density less than the remainder thereof.
 15. A gasket structure in accordance with claim 14 wherein said sealing bead is substantially semi-circular in cross section and is of sufficient size to effectuate substantially fluid-tight sealing when said structure is clamped and used in its intended environment.
 16. A gasket structure in accordance with claim 15 wherein a second gasket layer is provided on the opposite side of said heat-insulative member opposite said sealing bead. 17 A heat insulator gasket for carburEtors used in automotive engines and the like comprising a core member of fiberboard material, and gasket cover stock comprising elastomeric material bonded to the top and bottom faces of the core, said core and cover stock having a plurality of aligned openings therethrough for the reception of bolts, said bolt holes having the area immediately adjacent thereto characterized by having a density substantially greater than the density of the remainder of the gasket, at least one of said cover stock coverings having an elevated continuous bead lying in a plane above that of the densified bolt hole areas and located on and above said remainder of the gasket.
 18. A gasket as set forth in claim 17 in which the densification in the area of the bolt holes comprises a non-metallic, highly densified, resin-impregnated and cured material having a heat-insulating factor less than about
 3. 19. A heat insulator gasket for carburetors and the like comprising a core member carrying gasket members on the top and bottom surfaces thereof, and with bolt holes and a fluid port extending through the composite gasket, said gasket being characterized in that the gasket in the area of the bolt holes has a k factor less than about 3; the thickness of the gasket in such areas is greater than the thickness of the adjacent area of the gasket; a sealing bead is formed on one or both of the gasket members in the area of and surrounding said fluid port; and wherein the overall thickness of the gasket in the area of said sealing bead is slightly greater than that of the gasket at said bolt hole areas, whereby when the gasket is clamped between flanged members, an air space is provided between one of the flanged members and the adjacent gasket member.
 20. A gasket as set forth in claim 19 in which the core member is a cured, resin-impregnated, asbestos fiberboard.
 21. A gasket as set forth in claim 19 in which the air space is approximately 0.005 inch to 0.010 inch in depth.
 22. A gasket as set forth in claim 19 in which a sealing bead be provided on both the top nd bottom gasket members.
 23. A gasket as set forth in claim 19 in which the free height of the sealing bead is selected to provide about 0.005 inch to about 0.007 inch compression when the flanged members are clamped together.
 24. A gasket as set forth in claim 19 in which an additional protuberance is provided on one or both gasket members adjacent to the peripheral margin of the gasket. 